/Engine/Source/Runtime/RHI/Public/GPUDefragAllocator.h
Performs a partial defrag doing slow all chunk search to find used chunks to move that are surrounded by other used chunks That a freechunk walk won't find.
void PartialDefragmentationSlow ( [FRelocationStats](API\Runtime\RHI\FGPUDefragAllocator\FRelocationStats) & Stats, double StartTime )